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Three-way Review: HeadAmp AE-2 vs RSA Hornet M vs Rockhopper Mini³

post #1 of 53
Thread Starter 

More than 5 months ago, at the beginning of the summer, I had plans to do a multi-way review of the latest portable amps. 5 amps were going to be included. Amps I ended up tossing out and why:

- C&C Box v2, because Headb.com replaced this model with the Box+, and I didn't want to include an amp that was no longer available new.
- Go-Vibe V6, because Norm decided to stop making his amp line. Same reasoning as above.
- Xenos 1HA-EPC, because Xenos went out of business. Again, the same reasoning as above.

Flash forward to today. Sure there are lots of in-production portable amps now, and of course there are others I would've liked to include for this multi-way review, but couldn't due to lack of funds, like the Meier Audio HeadSix for one.

For reference, I also have experience with the iBasso T2 and Practical Devices XM4, reviewed here on Head-Fi and on StereoMojo, respectively.

Equipment Used

Power cord: Signal Cable Silver Resolution Reference
Source: Arcam FMJ CD33
Interconnect: Signal Cable SilverMini
Headphones: AKG K701 w/ Equinox, Audio-Technica ATH-AD2000
Amp reference points: HeadAmp Gilmore Lite LE (v2 w/ DPS) (solid-state) & Cayin HA-1A (tube)

Only my Equinox-recabled K701 was used because this headphone has always been my default reviewing tool due to its reference monitor-like sound and its scaling abilities. Also please note that I do not necessarily recommend that any of the reviewed amps and the K701 should be used together - on the contrary, I feel they should not be used together for general listening. The difference between the reviewed amps and the HeadAmp Gilmore Lite is wide enough that I instantly recommend the Gilmore Lite over them.

Burn-in hours on the amps: 400+ on AE-2, 400+ on Hornet M, 12 on Mini³ (will burn in more and update later).

Evaluation CD Tracks

Alison Krauss - Lonely Runs Both Ways - "Goodbye Is All We Have"
Massive Attack - Mezzanine - "Inertia Creeps"
The Crystal Method - Vegas [Deluxe Edition] - "High Roller"
Thievery Corporation - The Mirror Conspiracy - "Samba Tranquille"


(click for larger versions)

Part 1 - Creeped Out

On Massive Attack's "Inertia Creeps," the three amps portrayed this track in interestingly different ways.

The AE-2 gave the most 3D soundstage with a large sense of air, as well as throwing everything into convincing alignment in front and off to the sides and between. A good sense of depth too. Bass went the deepest between the three - though not the most powerful, simply the deepest. Timing on the belly drums was wholly accurate and gave the entire sound of the impact - from the initial slam to the fast decay of the membrane. The opening effects of this track (not sure what they are exactly) also came out the clearest - there was absolutely no blurring, simply crystal clarity on the mysterious notes as they give way to the imminent belly drum. 3D's vocals also sounded the most intact from top to bottom, with no unnecessary emphasis on the "clearly", "nearly", and other synonyms.

The Hornet M went in a different direction to provide a more visceral, fronted presentation. Not as 3D, but almost as wide as the AE-2. Impact on the belly drum was noticeably harder, as if being hit with 150% more force. The overall sound of the track felt harder and a tad more aggressive on the bass - it had more of a self-assured, confident step to it than the AE-2. This confident vibe made the track sound even more foreboding and creepy than what it already is, making it sound even more like a march of the evil minions or cockroaches from the underworld (I've always felt this track to sound like that). Where the Hornet M fell back compared to the AE-2 was overall clarity - it blurred a portion of the tiny details buried in the track, and the opening creepy notes too.

The Mini³ ended up being pretty disappointing. It didn't convey enough agility and speed, as it didn't spring off the belly drum as well as either the AE-2 or Hornet. It too blurred some of the detail on the track, but at more than the level of the Hornet. A shorter-than-normal decay seemed partially the reason for this, as the belly drum lost some of its after-effect on the Mini³. In its favor though it did exude power and strength, along with a good, strong, anchored bass component. Among the three, the Mini³ exuded the most bass power and character - strong, almost borderline to a little too much bass for my liking. Though this may certainly be preferential for those who like bass.

Part 2 - Sizzlin' Samba

Different takes again on Thievery Corporation's "Samba Tranquille."

The AE-2 was the most agile, lithe, & articulate. Effortlessly sprung from one note to the next leaving behind nothing but crystal clarity. Accurate on both the percussion hits and the double-bass - no overdoing of anything, just simple & faithful enough to sound realistic. There was also plenty of air around the instruments - the most among the three, in fact. It was also the most spatial, retrieving the most room acoustics of the three.

The Mini³ wasn't quite as clean but translated just the right amount of energy. And there were a couple things it conveyed that the AE-2 didn't - like the acoustic bass on the 4th beat and a backwards positioning push on the percussion layer. Deep, throbbing bass, and again the most of the three.

The Hornet gave a disparate "disconnected" feel between the double-bass and the percussion layer that didn't quite feel realistic. The percussion was placed a bit too far away from the double-bass that they sounded too separate from each other. Not quite as quick on the take as either the AE-2 or the Mini³ either, as it sounded just a tad slow in grabbing the lead of impact on the percussion. The Hornet also sounded the most in-your-face of the three amps with the most direct presentation, and gave the percussion hit some extra force too, about 150% more.

Part 3 - Low and Lower

I'm well aware that the K701 is not ideal for evaluating bass. However, the Equinox re-cable does improve both extension and decibel output in the lower regions. And I've compensated for the K701's deficiency in this area too.

That said, the low, low, LOW bass on Crystal Method's "High Roller" was best translated on the Mini³, BY FAR. From what I could tell with the K701, it went just as deep as both bass lines (there are two active ones throughout the track) and brought forth power, authority, depth, force. I bet if I heard this on the Audio-Technica AD2000, it'd be the kind of yawning bass that seems like it's seeping up from the netherworld. The sweeping undercurrent on both active bass lines was amazing. It reminded me of the Portaphile V2^2 Maxxed which also had this kind of bass.

The AE-2 and Hornet M effectively tied for next best bass output. They went in different ways, as expected - the AE-2 went the way of reaching lower, while the Hornet M went more the way of being leaner but still low enough. The AE-2 did seem to reach just a tad lower than the Mini³, but at the expense of sweeping power - it just didn't "ooze" enough. And the Hornet had a bit of a hard time reaching as low as either - it certainly tried and put up a valiant effort, but it just couldn't get to the low, LOW bass of this track. For those guys who know this track, you know what I mean - this track is best experienced on a giant subwoofer, not headphones. The Hornet M didn't ooze low bass either, but it did call up some quality speed and maintained good distinction between the various bass layers.

Part 4 - Class & Finesse

Finally on something much less challenging, Alison Krauss' "Goodbye Is All We Have" sounded great on all three! How do you differentiate between three great-sounding renditions? By paying attention to certain subtleties, that's how.

As before, the AE-2 once again proved that it's a master at what it does - preserving layers of air, especially the ones surrounding the performers. The soundstage it created was simply alight with air and space - the resulting open soundstage simply sucked me into it, because if there's one thing I love, it's soundstage, and lots of it! And the layers of instruments were all there for the listening and exploring. Specific to Krauss' voice, if there's one thing the AE-2 nailed about it, was the fragility in it. Krauss' voice is a lot of things, including fragile, and the AE-2's character allowed it to capture that part of her voice with ease.

The Mini³ brought the various layers of the music laterally together so it sounded more compacted in - not that it sounded compacted in, only in comparison to the AE-2, like the guitar on the right moving in, and Krauss herself a little more right and center and not out & away so much. A more intimate performance in other words. Still some very good spatials though, with good delineation between the performers, though not as much in the way of depth as the AE-2. On Krauss' voice, the Mini³ captured the angelic purity the best among the amps - perfectly toned and textured and sweetened over.

The Hornet M did something completely different. It went after the layers comprising Union Station and gave them greater heft and weight. Fuller, heavier, and with extra body, for ultimately probably a more realistic sound. A pleasantly warm mid-range - direct and involving, and it gave the K701 some very welcome flavor. Laterally, about the same as the Mini³, except just a tad smaller. Probably the most intimate performance of the three amps, and really just an overall warm and affecting sound. And as for Krauss' voice, on this track it's also almost sultry, and the Hornet M captured that part the best, also enhancing the femininity and come-hither quality in it.

Part 5 - Torture Tests

With an idea of what the amps sounded like, of course I had to subject them to some of my most brutal CD tracks to see how far they could stretch, right?

For the AE-2, I gave it Laika's "Bedbugs" and "Martinis on the Moon" from Sounds of the Satellites, to test for frequency response and completeness of soundstage. My previous amp reference for this track was the GS-X. Could the AE-2 withstand it too? Well, it only partially succeeded. In some aspects the AE-2 fell flat. There was too much bass quantity on the "Bedbugs" bass rhythm that it felt bloated and not controlled enough. The spatials also felt unnaturally compressed in the vertical direction, and there wasn't enough tight control over some of the fast details. It didn't feel fast or spontaneous enough. The AE-2 didn't hit fast enough on a percussion hit on "Martinis on the Moon" either. Fortunately it got most of the circular-traveling guitar. But in terms of precision and control, the AE-2 is simply outclassed by the cheaper Gilmore Lite!

For the Mini³, I spun Crystal Method's "Murder" from Tweekend. Oops. While it dug down low enough to make the bass line oppressively heavy (only 1 of 2 counts), the amp pretty much failed the second part, as it failed to pick up the top of the two-way bass phase (the K701 doesn't extend low enough to get it all) and instead made it sound more like a generic one-note thing. On "Ten Miles Back" on the same disc, there's an ongoing bass pulse that rips through the floor when played on a subwoofer. Of course it's not fully rendered on the K701 but the K701 does get a good chunk of it on the Gilmore Lite. The Mini³ didn't meet the Gilmore Lite's level of extension there either - almost, but not quite. The Mini³ also seemed to exaggerate the bass both on this track and the following one "Over The Line." The K701 makes it pretty easy to tell when an amp is boosting its bass anywhere in its spectrum and the Mini³ definitely gave more quantity than the Gilmore Lite, in the region between 30 and 50 Hz. Not that it's a bad thing of course, but worth noting.

For the Hornet M, I wasn't sure how to "torture test" its mid-range, so I gave it Eva Cassidy's "I Know You By Heart" from Songbird, Zero 7's "Home" from When It Falls, and KT Tunstall's "Under The Weather," "Silent Sea," and "False Alarm" from Eye to the Telescope. On these CD tracks, you don't need a warm-sounding amp to add warmth, they're already that way. Well, the Hornet M added enough mid-range swarth to these tracks that it made them a bit too sleep-inducing, and bit too over-the-top that it unbalanced from the treble and bass. Not that either was lost, but the added mid-range was too distracting. I guess the lesson from this is to not put the Hornet M in a system that's warm-sounding.

Part 6 - Mini³ Burn-in

Parts 1-5 of this review were written when the Mini³ had only 12 hours on it, so I burned it in for over 120 hours and then came back to it on the same CD tracks above.

The amp showed definite signs of improvement after the 120 hours of burn-in. It became better able at catching detail with increased attack, and increased treble snap. Not as much air around it as the AE-2, but an improvement nonetheless from its previous state. "Inertia Creeps" and "Samba Tranquille" gave cleaner and more precise edges on the belly drum and percussion (respectively), and the frequency response overall shifted a teeny bit more in the direction of balance - slightly leaner bass but still just as low and powerful.

Part 7 - Bass & Efficiency Test

I was able to test these amps on an Audio-Technica ATH-AD2000, so I decided to put them up against some reference bass tracks from my CD collection - The Crystal Method's "Murder" and "Over The Line" from Tweekend, and Massive Attack's "Black Milk" from Mezzanine.

As expected, the Hornet M provided the most visceral, thickest bass of the amps. While it didn't exactly ooze around at the limits of the AD2000's extension, it did give it a hard, plentiful impact - though I'd say it was overdoing it, the bass just seemed out of balance with the rest of the spectrum. The AD2000 is a mid-range focused headphone and the Hornet M made it sound mid-bass focused.

The AE-2 surprised with extension down to the low undercurrents. A landslide of an improvement from HeadAmp's previous AE-1 in fact, which had a noticeable recession in the low bass. Not so on the AE-2. While it did give the leanest bass of the three amps, it had the best control - firm with restraint, and absolutely no flab, boom, or excess.

The Mini³ gave that extra modicum of "push" around the mid-bass to add balance to the AD2000's bass signature. Not too much to make it sound slow or thick, but enough to also make it plentiful, as did the Hornet M.

And then of course, the AD2000 lends itself to two kinds of efficiency tests, so I did both:

First, I checked the amps for noise at max volume with max gain (where configurable). The Hornet M was not completely silent at max volume on High gain and had a slight detectable machine hum. Its volume pot was also slightly scratchy as it was turned up. On the flip side, the Mini³ (gain of 2) and AE-2 (High gain) were both completely silent, with no discernible effect as the volume pot was turned up.

Second, I set the Hornet M and AE-2 to Low gain to see how controllable the AD2000 was with music playing. There was a decent level of control on the Hornet M and Mini³, but the AE-2 easily took top place - on Low gain, it simply provided the smoothest volume gradations and allowed for very fine control. It also gave the most headroom on the volume pot before the AD2000 got loud at the same SPL as on the other two amps. In contrast, both the Mini³ and Hornet M just didn't compare. Their low gains were useful enough for the AD2000, they just didn't provide enough fine-tuning.

Part 8 - AE-2 vs Mini³ Update

A post-week update on the Mini³ against the AE-2 with the Mini³ at over 200 hours. I went back and listened to both amps on some new CD tracks - Laika's "Widows' Weed" from Good Looking Blues, Alison Krauss & Union Station's "The Road Is a Lover" and "Little Liza Jones" from So Long So Wrong, and The Crystal Method's "Busy Child" from Vegas [2007 Deluxe Edition].

I found the two amps closer than I thought I would. Not quite "neck and neck" per se, but the Mini³ sounded quite close to the AE-2 in terms of proficiency. It picked off a surprising amount of detail from the Laika track - quick & agile it was, as it easily picked off the various digital effects, warbles, and the high-pitched noises. Very clear sound overall, with very realistic positioning. A wide soundstage, though not very deep, as it gave more of a lateral, in-front presentation. The AKUS tracks backed this up as well, as the band sounded closer on this amp than it did on the AE-2. The Mini³ also captured a great deal of mid-bass detail, including the snap, impact, & thump of the acoustic bass. It did have a fuller mid-bass/lower-mids presence than the AE-2, allowing the band to sound more natural and realistic in tone. However, it was obvious that the Mini³ just wasn't as as agile & fast as the AE-2. The AE-2 simply and clearly had the faster attack, as it was better able to separate the very fast sequences of banjo notes on "Little Liza Jones" - both the forward & backward pluck along with the instantaneous "pop" associated with each. The Mini³ came close, but simply wasn't as fast, it blurred a tiny part of the forward & backward plucks, and just barely got the tap of the strings.

I again found the AE-2 to have the overall edge in soundstage and clarity on these tracks as well. It was clearly and immediately more open-sounding, with greater projection, and less in-front sound, gravitating more towards out and away, which it should be on the Arcam FMJ CD33. It was especially noticeable on the Laika track, as it sounded more expansive, less restrictive. More "breathing room," as if the Mini³ were almost in a bubble or vacuum. The AE-2 also brought out the various layers into more exact detail and distinctiveness than the Mini³ - of all the layers in this track, it was much easier to pick out any one of them on the AE-2, as they didn't get "buried" as much.

And I do want to note that the AE-2 did sound a bit on the thin side compared to the Mini³, which gave more an impression of a flat response, as that amp just had the fuller, bodied sound. The AE-2 didn't give as much tone and body to instruments, and actually sounded laid-back and calm in comparison.


I come from primarily AC-powered home amps, so when I listen to a portable, I hope to get at least most of the "home amp" type sound, or as much as possible.

In that aspect, the AE-2 performed the best, at near 67%-75% the sonic performance of HeadAmp's GS-1. That might seem low, but the GS-1 is in a high class of amps, and a portable that can get as close as that is very impressive. At less than half the price, the AE-2 is simply a superb value - the same basic wire-with-gain sound, with no major subtractive or additive qualities. Detailed, clear, with very good frequency balance, and the most spatials in the group with an open 3D soundstage. Add in its features - the 3-way gain, alternate RCA jack input, loop out (the unused input becomes the loop out), 30-hour Li-Ion battery, and power enough to almost drive even the K340, and you have a top-notch amp (with top-notch build quality too) that can easily pull double-duty in a home rig. Stick it on a good source and it opens up even more.

The Hornet M was my first foray into Ray Samuels' amps and after hearing it, I have to say that it has a great sound indeed. It has a tonal richness, a very pleasantly warm mid-range, lots of character. However, its character can be obtrusive on either warm-sounding equipment or warm-sounding music, and the key areas where I found it lacking were detail, and extension & quantity at the frequency extremes.

In a turnabout from my previous opinion, I think the Mini³ is a fantastic value at $125. There is some competition from the Practical Devices XM4 which has an even cleaner and more clinical sound, and can roll op-amps, and is armed with other features, but in terms of sound overall, the Mini³ gains the edge with a flatter response, as the XM4's response is more uneven. Low, powerful bass balanced with a bodied mid-range and finely controlled treble. It certainly has its drawbacks but for non-critical listeners, it's the best-sounding portable I'd recommend for under $200.
post #2 of 53

what a tease!
post #3 of 53
Can't wait for it. Looks like it'll be interesting, given the inclusion of the mini^3.
post #4 of 53
Hilarious actually. I can't wait to see what Asr thinks.
post #5 of 53
Here's a prediction. AE-2 slightly > Mini^3 (Though pretty close) while both >> Hornet.

Which is what I'd go with ;p Definitely curious about your conclusions though Asr!
post #6 of 53
Thread Starter 
I don't usually rank components in multi-way reviews, Icarium. It's unlikely I'll do that here.
post #7 of 53
Aww ;p No fun.
post #8 of 53
Originally Posted by Icarium View Post
Here's a prediction. AE-2 slightly > Mini^3 (Though pretty close) while both >> Hornet.
Haha, you went ahead and ruined the fun! Actually it's more like ">>>". (I mean, considering the Hornet is just a...)
Asr, be as critical of these amps as you can! Haha

post #9 of 53
I like those orange LED's, but green is pretty nice too.

That Ray Samuels rig is really small!!

post #10 of 53
Wow... nice... post it now!!! LOL
post #11 of 53
post #12 of 53
This' going to be real cool !!!! ... specially the Hornet vs. AE-2. It's going to give me a vague sound signature of the Predator vs. the Pico.

post #13 of 53
Thread Starter 
Part 1 of this four-part review is now up.
post #14 of 53
Originally Posted by Asr View Post
Part 1 of this four-part review is now up.
Nice startup. I think I started to see the lights.
post #15 of 53
Interesting and well written review ASR, you're observations and ability to convey them gave me a very good sense of the different amps characters. Of course being familiar with one of the amps did help help put your thoughts in perspective and for the most part agree with your assessment of that amp (the AE-2).

I do wonder at the wisdom of solely using the K701's for review purposes (especially now, given the disturbing trends thread). Considering these are primarily portable amps and the K701's are said to be fairly hard to drive primarily home headphones would the results be skewed in any way when easier to drive portable oriented headphones are used? Don't get me wrong, I'm not saying I think you were wrong to use the K701's if that's your overall reference tool, just at the wisdom of not including at least one other headphone that might be more reflective of what would typically be used with these amps.
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